Breath-Taking Popcorn

To most people, the scent of hot buttered popcorn brings to mind excursions to the local movie theater for big-screen viewings or recalls quiet winter respites before a crackling fire. To those who toil in the plants that package microwave popcorn, the same smell can not only be overpowering but also signal lung dangers, according to a new study.

Researchers with the Missouri Department of Health and Senior Services initially investigated a report of eight cases of serious lung disease among former employees of a microwave-popcorn factory. Half of these were mixers—workers who add salt and flavorings to tanks of soybean oil. The air at their workstation not only carried a strong buttery odor but also bore a cloud of visible dust. The other four workers came from popcorn-packaging stations 15 to 90 feet away. The rate of lung disease turned out to be about 31 percent for mixers, 1 percent for packers, and zero elsewhere in the plant.

All eight affected former employees exhibited lung damage "resembling bronchiolitis obliterans," the researchers found. This rare yet severe disease—which has often been linked to inhalation of occupational chemicals—can result in coughs, labored breathing, and airway obstruction that doesn't improve with the use of bronchodilators. In most cases, the disease is irreversible.

Buttery air pollution

Together with investigators from the National Institute for Occupational Safety and Health, researchers with the Missouri health department sampled air throughout the plant and noted how many workers were stationed in each area. They also tested 117 current plant workers for their capacity to move air in and out of their lungs.

Their findings, reported in the April 26, 2002 Morbidity and Mortality Weekly Report, show that "current workers had two to three times the expected rates of respiratory symptoms and self-reports of physician diagnoses of asthma or chronic bronchitis." Overall, the occurrence of obstructed airways was 3.3 times that typical for individuals the same age and with the same smoking habits.

Pollution sampling turned up roughly 100 volatile organic chemicals in the plant's air. The scientists used diacetyl, a compound responsible for buttery smells, as a marker for exposure to workplace chemicals. Concentrations of diacetyl ranged from 10 parts per million (ppm) in the air breathed by the plant's 13 mixers to 1.3 ppm in the packaging area, where another 276 people worked, to just 0.02 ppm elsewhere in the factory.

An editorial accompanying the new report states that the "results of this investigation raise concern about possible risk for workers in other flavoring and food production industries." Indeed, it notes that the Centers for Disease Control and Prevention has uncovered another case of fixed-airway obstruction in a microwave-popcorn-manufacturing worker, this time in Nebraska, and additional cases at a flavoring-manufacturing plant.

The editorial offers evidence that popcorn plants may pose special risks. Follow-up animal studies by CDC suggest "severe damage" to tissues lining airways after inhalation of high concentrations of a buttery flavoring used in the Missouri popcorn factory. CDC plans studies to home in on the active agent.

And what about those of us who pop corn in our microwaves, scenting the house for hours with a buttery smell? According to that editorial: "CDC has no evidence to suggest risk for consumers in the preparation and consumption of microwave popcorn."